360 ON THE NUMBER OF POLAR BODIES AND 



splitting of these loops appears to me to be almost a proof of the 

 existence of such an arrangement, for without this supposition the 

 process would cease to have any meaning. 



This is the only kind of karyokinesis which has been observed 

 until recently; but if the supposed nuclear division leading to 

 a reduction in the number of ancestral germ-plasms has any real 

 existence, there must be yet another kind of kaiyokinesis, in 

 which the primary equatorial loops are not split longitudinally, but 

 are separated without division into two groups, each of which forms 

 one of the two daughter-nuclei. In such a case the required reduc- 

 tion in the number of ancestral germ-plasms would take place, for 

 each daughter-nucleus would receive only half the number which 

 was contained in the mother-nucleus. 



Now there is more evidence for the existence of this second kind 

 of karyokinesis than the fact that it is demanded by my theory ; 

 for I believe that it has been already observed, although it has not 

 been interpreted in this sense. 



It is very probable that this is true of van Beneden's l observation 

 on the egg of Ascaris megalocephala : he found that the nuclear 

 division which led to the formation of the polar body differs from 

 the ordinary course of karyokinesis, in that the plane of division 

 is at right angles to that usually assumed. Carnoy 2 has confirmed 

 this observation in its main features, and he has made the further 

 observation that out of the eight nuclear loops which are found at 

 the equator of the spindle, four are removed with the first polar 

 body, and that half of the remaining four are removed with the 

 second polar body. The first of these two divisions would have to 

 be looked upon as a reduction, if it is certain that each of the eight 

 nuclear loops consists of different ancestral germ-plasms ; but this 

 assumption is impossible, although on the other hand it cannot be 

 directly disproved : for we are not able to see the ancestral germ- 

 plasms. But it must nevertheless be maintained that the removal 

 of the first four loops does not imply a reduction in the number of 

 ancestral germ-plasms in the nucleus ; because, as I have already 

 argued, two successive divisions of the number of ancestral germ- 



1 E. van Beneden, ' Recherches sur la maturation de 1'ceuf, la fecondation et la 

 division cell ulaire.' Gand et Leipzig, Paris, 1883. 



2 J. B. Carnoy, ' La Cytodterese de 1'ceuf, la ve"sicule germinative et lea globules 

 polaires de 1'Ascaris megalocephala.' Lou vain, Gand, Lierre, 1886. 



